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73ish Raleigh Gran Sport - Seat post diameter help

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73ish Raleigh Gran Sport - Seat post diameter help

Old 10-01-09, 10:14 AM
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73ish Raleigh Gran Sport - Seat post diameter help

Does anyone know what seat post size is correct for a 1973ish Raleigh Gran Sport? The seat post that was on mine is too small.

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Old 10-01-09, 11:33 AM
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Butted 531 seat tube = 27.2 mm.
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Old 10-01-09, 11:45 AM
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Non butted could come in a number of sizes. 26.8 is fairly common, but 26.6 and 26.4 are also possible. What do you have that's too small?
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Old 10-01-09, 12:14 PM
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The post on my '72 that (sigh) used to look like yours is 27.2.
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Old 10-01-09, 03:41 PM
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I don't know what diameter the post I have is... but I do know that the gap in the back of the seat lug closes up completely with that seat tube in place. I need to go buy some digital calipers soon.

I am going to run this by the old school LBS soon but I wanted to get an idea of what it might be before I go.

Thanks for the help!
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Old 04-01-10, 07:05 AM
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OK, I'm going to bump up this old thread now that I have new info. I bought some (cheapo) digital calipers to read the sizes.

- The reynolds 531 sticker simply says "butted" so I imagine that it is single butted tubing.

- The seatpost measured around 26.4mm

- I have a shim installed

- I seemed to get 26.8 by measuring the inside diameter of the tube

This seat lug has been abused in the past so I wouldn't doubt if its ovalized. Here is a picture of the back of the seat lug, I always thought it looked squashed. You can see the small crack from the previous owner before I inserted a shim.

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Old 04-01-10, 08:29 AM
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Originally Posted by mkeller234 View Post
- The reynolds 531 sticker simply says "butted" so I imagine that it is single butted tubing.
Reynolds tubing stickers either say the tubes are butted, or not. They never say double butted (which would mean butted at both ends) nor triple butted (butted at all three ends) or quadruple butted (wtf?).

If your tubing matches your sticker, your tubes are butted 531, AKA "double butted," and you want a 27.2 mm seatpost. If someone has put a smaller post in there and tightened the clamp down, then for sure the top of the tube is misshapen by now, so a 27.2 won't fit without a little work. I have a chromed steel 27.2 post I'd try with a lot of lubrication and a little force, after which I'd expect an aluminum 27.2 would be fine.
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Old 04-01-10, 09:29 AM
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I'm 99% sure my similar era Grand Sports (yes, that's what it says on the top tube) takes a 27.2mm post. I can measure when I'm home.

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Old 04-01-10, 10:02 AM
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How many butts did you say were on the seatpost?
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Old 04-01-10, 12:41 PM
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That is exactly what I was afraid of. I'll have to look around for a 27.2 post to work into it.
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Old 04-01-10, 03:33 PM
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Does anyone have tips on how to gently expand the seat cluster. I was thinking a lot of grease and the careful use of a flat blade screw driver. Maybe a rubber mallet and maybe insert post sizes working my way up to 27.2.
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Old 04-01-10, 04:03 PM
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Ok, I got a 27.2 post in without much of a fight. It looks much much better to me than it had. Now I have to search for an appropriate 27.2 post for this bike, anyone have one? Thanks for the help guys!

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Old 04-01-10, 07:12 PM
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Fwiw, I did confirm that mine takes a 27.2mm post. In terms of originality, it probably came with a straight pin alloy post (or at least mine did). Is that what you're looking for, Matt?

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Old 04-01-10, 08:08 PM
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Originally Posted by nlerner View Post
Fwiw, I did confirm that mine takes a 27.2mm post. In terms of originality, it probably came with a straight pin alloy post (or at least mine did). Is that what you're looking for, Matt?

Neal
Yeah, looking at the catalog that is what it had. I moved a little fast this afternoon and bout a 27.2 inline alloy post from Niagara cycle works. It was cheap and aluminum, I figure it can't be that bad. Thank you for measuring your post Neal. I haven't ridden this bike much mainly because I was worried about the post. Now with the weather warming up I am making some changes and hope to ride it more this year.

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Old 04-01-10, 08:10 PM
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Man, I should post a newer picture of my bike. The one up top looks really bad.

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Old 04-01-10, 08:24 PM
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Fantastic! I wouldn't worry too much about installing a good quality post. I think anything is better than those straight posts with the removable clamp.

I thought of your bike before I installed white Planet Bike Cascadia fenders on my Centurion. I'm glad that I did it. Good match on the bar tape, too.
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Old 04-01-10, 08:46 PM
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Originally Posted by DiegoFrogs View Post
Fantastic! I wouldn't worry too much about installing a good quality post. I think anything is better than those straight posts with the removable clamp.

I thought of your bike before I installed white Planet Bike Cascadia fenders on my Centurion. I'm glad that I did it. Good match on the bar tape, too.

Ha, well I am borrowing a Campy Record post from another bike right at the moment. I actually ordered one of the straight posts to keep with the original equipment, I actually like how it looks on this bike too. The bar tape ended up being a happy surprise, so much that I went back and bought eight rolls! I saw the fenders on your bike and actually didn't know they came in white. That's good to know too since I may want some in the future.
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Old 04-01-10, 09:33 PM
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Planet Bike doesn't have them on their website. At least not a month ago. I was surprised to find them in a store locally. They don't have the huge 8" x 1" logo that my silver set does. Just a tiny relief in the mudflap that I hadn't even noticed on my silver set due to the more obvious gorilla in the room.

I didn't mean for that to be a disparaging remark about the seatpost. Being poor and unsophisticated most of my life, I've only recently learned about nice seatposts, so I'm a little overzealous. I would never throw away one of those posts, but in the absence of a post (especially in the now common 27.2 mm size) I'd probably splurge on a nice one. Either way, amazing bike!
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Old 04-01-10, 09:35 PM
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You might want to drill a hole into that crack - enough so that it doesn't get longer.

-Kurt
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Old 04-01-10, 09:39 PM
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Originally Posted by DiegoFrogs View Post
I didn't mean for that to be a disparaging remark about the seatpost. Being poor and unsophisticated most of my life, I've only recently learned about nice seatposts, so I'm a little overzealous. I would never throw away one of those posts, but in the absence of a post (especially in the now common 27.2 mm size) I'd probably splurge on a nice one. Either way, amazing bike!
Oh, it wasn't taken that way at all. I usually wouldn't pick a post like that either. I splurged on a saddle bag this afternoon so I have to take it easy with the seat post for now.
I got one of these Zimbale bags, can't wait to get it:

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Old 04-01-10, 09:40 PM
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Originally Posted by cudak888 View Post
You might want to drill a hole into that crack - enough so that it doesn't get longer.

-Kurt
No april fools in that is there?
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Old 04-01-10, 09:45 PM
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Originally Posted by mkeller234 View Post
No april fools in that is there?
No April Fools. Why do you think AVA stems crack at the slot?




...and if you look at many other machines, you'll find they've had one added, either in the tube, or in the lug, wherever the slot ends:



-Kurt
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Old 04-01-10, 10:14 PM
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Outstanding bag... Yeah, I cheaped out on the bag and went with the $60 Origin-8. Functional, but poor craftsmanship.

FWIW, my "good" seatposts are the cheapest Kalloy and a Japanese clone of the Campagnolo that Kurt posted above. As a consummate tinkerer, I'm loving the adjustability of the Japanese post. I've ridden cheap chromed steel posts until about two years ago when I bought a bike sans post, and thus the Kalloy.
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Old 04-02-10, 01:13 PM
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Kurt, I'll give that a shot. My Pro was made the way you described. Any tips?
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Old 04-02-10, 01:43 PM
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Originally Posted by mkeller234 View Post
Any tips?
Get a good drill bit.

-Kurt
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